DISTRIBUTION AND EXCRETION OF LANTHANIDES - COMPARISON BETWEEN EUROPIUM SALTS AND COMPLEXES

Europium (Eu-152,Eu-154) was intravenously injected into rats as: (i) the chloride salt at pH 7.4, (ii) the chloride salt at pH 3, (iii) the albumin complex and (iv) the DTPA complex, and tissue uptake was dete rmined 24 h later. For the chlorides, the target organ for uptake was liver (about 60% of dose) whilst europium complexes were rapidly excre ted in urine and were predominantly taken up into the kidney (about 0. 5% of dose) and bone. Liver uptake of EuCl3, pH 7.4, corresponded to t hat of a colloidal material with most Eu-152 present in the non-hepato cyte population; however, EuCl3, pH 3, was handled in a different mann er, with significant uptake by hepatocytes. The differing tissue distr ibutions of EuCl3 and Eu-albumin suggest that plasma albumin does not readily bind injected EuCl3. Renal uptake of europium, although a rela tively low proportion of the injected dose, was associated with many s ubcellular fractions, including lysosomes, suggesting significant intr acellular uptake and thus possible retention.